Model card · Released
Hemmingway-1.5
The undetectable AI. It passes the world’s best AI detectors 90% of the time, at every thinking level, more often than real human writing does.
Passes AI detectors
We tested it on 1,848 texts in 13 kinds of writing, at every thinking level. Every one a first try: no picking, no retries. Higher is better.
| Model | Passes |
|---|---|
| Hemmingway-1.5 | 92 |
| Fable 5.1 | 26 |
| GLM-5.3 | 21 |
| GPT-6 Astra | 20 |
| Kimi K3 | 18 |
| Qwen3.8 Max | 18 |
| DeepSeek V4 Pro | 13 |
| Thinking | Passes |
|---|---|
| Off | 90 |
| Low | 90 |
| Medium | 90 |
| Extra high | 90 |
| Kind | Passes |
|---|---|
| Product descriptions | 100 |
| Blog posts | 96 |
| Forum comments | 96 |
| Stories | 94 |
| Speeches | 94 |
| Emails | 93 |
Hemmingway-1.5Other models
The detectors are GPTZero & Pangram and four of the top open AI-detector models: Fakespot from Mozilla, Vanguard, WasItAIGenerated and MELD. A text passes when they read it as human with at least 90% confidence. The human writing is 1,670 emails, essays, blog posts, reviews, stories and comments written by people. How the test was run, and what changed from Hemmingway-1.
Real outputs
Reads as humanEmail
Write an email inviting the team to a farewell lunch.
We would like to invite you all to a farewell lunch on Wednesday next week (the 26th). Please come if you can; we’re going to Gino’s and I’m buying.
Date: Wednesday 26th April
Time: 1pm – 2.30pm
Place: Gino’s
I need to know who’s coming as soon as possible, so please reply to me.
See you there
Jackie
Reads as humanEmail, rewritten
Humanize this text:Subject: Heating Issue - Unit 2B Dear Mr. Thompson, I am writing to inform you that the heater in my apartment (Unit 2B) has stopped working. It turned off yesterday evening and has not restarted. The temperature in the unit has dropped significantly, and it is becoming uncomfortably cold. Could you please arrange for someone to look at it as soon as possible? I can be home all day tomorrow if that helps. Thank you, Rachel Okafor
The heater in my apt (2B) quit last night and will not come on. The apt is getting very cold. I’d appreciate it if you could have someone come and take a look at it ASAP. I’ll be home all day tomorrow. Thanks so much. Rachel Okafor
Reads as humanForum comment
Write a Hacker News comment on the thread “Ask HN: What can I do to get into a good MSc program from an unknown university?”.
Look for any opportunity to do research work alongside professors. If you can co-author papers that would be even better. You’ll also want a good statement of purpose and ideally, recommendation letters from professors that supervised you for research work.
If the program is entirely coursework-based and you have relevant work experience, you can even skip the recommendation letters.
Reads as humanProduct description
Write a product description for a handmade ceramic coffee mug.
Handmade from Colorado red clay. Glazed in one of our own mixed colors, produced in small batches for true color variations. Please enjoy the little flaws. 12 oz (500ml). Dishwasher and microwave safe.
Reads as humanReview
Write an Amazon review for a vacuum cleaner that broke after a month.
Returned Product via Amazon
The product worked for a month before I heard the brush starting to grind and now won’t run at all. I’ve had a Bissell All-in-One machine for 4 years with no problems so I will be going back to Bissell (when I ever can find them in stores). The floor finish is nice though. 3 stars as it did clean fine for that month.
Reads as humanSocial post
Write a short Facebook status about our new puppy.
New puppy!! Holly had a litter of chihuahuas today, 6 puppies, and we decided we needed one so now we have Ben Fushi!!
The facts
- Size
- 27B
- Released
- 25 October 2026
- Built on
- Hemmingway-1, our first model (itself built on Qwen3.8-27B)
- Built for
- Anything that should read like you wrote it: emails, posts, reviews, product listings and stories. Write from scratch, or paste in AI text to make it sound like a person.
- Made by
- Hemmingway AI (Pty) Ltd
- Weights
- Open, on Hugging Face
- Licence
- CC BY-NC 4.0, free for non-commercial use. Commercial use by agreement: luka@hemmingway.io
- Context
- 262,144 tokens
- Settings
- Temperature 1.0, any thinking level. A lower temperature reads as more AI.
- Run it
vllm serve HemmingwayAI/Hemmingway-1.5 --max-model-len 262144
In the API
- Longest reply
- 32,768 tokens, thinking included
- Tools
- Function calling, in OpenAI's format
- API
hemmingway-1.5, OpenAI-compatible, and the default- API price
- $0.24 in, $0.024 cached in, $0.90 out, per million tokens.
- Where
- The Hemmingway app on Mac, Windows, Android and the web, where it is the default, and the API
Read more
The Hemmingway-1.5 release
What changed from Hemmingway-1, how the detector test was run, and where to get it.
Read itAll our models
Every Hemmingway model side by side, and how to pick.
See themRun it on your own hardware
The open weights, served with vLLM or Transformers, and the memory a 27B model needs.
Read itHemmingway-1
Our first model, the one Hemmingway-1.5 is built on, with its benchmark scores.
See its cardUse Hemmingway-1.5
In the Hemmingway app, free to try, through the OpenAI-compatible API, or from the open weights.